There is a difference between responsible criticism that aims for success and defeatism that refuses to acknowledge anything but failure. Hindsight alone is not wisdom, and second-guessing is not a strategy.
But what help from these fineries or pedantries? What help from thought? Life is not dialectics. We, I think, in these times, have had lessons enough of the futility of criticism.
The sceptic will say, 'It may well be true that this system of equations is reasonable from a logical standpoint, but this does not prove that it corresponds to nature.' You are right, dear sceptic. Experience alone can decide on truth.
Either criticism is no good at all (a very defensible position) or else criticism means saying about an author the very things that would have made him jump out of his boots.